1. Field of the Invention
The present invention relates to a linear stepping motor provided with a driving-guiding mechanism for maintaining a movable member in noncontact state by means of attractive force of electromagnets and also driving and guiding the movable member.
2. Description of the Prior Art
For achieving a linear movement, there has conventionally been employed a device in which a table, provided with a guide mechanism involving mechanical contact and a driving mechanism utilizing a ball screw on a motor shaft, is moved for example on a stationary surface plate. Such a device inevitably generates dust particles by the abrasion, since the frictional contact of component parts is unavoidable. The dust particle generation is a major problem in case such a device is used in a clean room as a positioner or a conveyor for a precision work such as manufacturing of integrated circuits.
Thus, in order to eliminate the mechanical contact, there has been proposed a fluid pressure guide, in which pressurized fluid such as oil or air is present between a stationary part and a movable part and maintains a small gap therebetween by the static pressure of said fluid. Such a guide is driven for example by a linear motor and is free from the drawback of dust particle generation.
However the above-explained fluid pressure guide is still associated with the following problems:
(1) As the distance between the stationary part and the movable part is generally as small as 5-10 .mu.m, the mutually opposed surfaces thereof have to be entirely finished with a very high precision;
(2) In case of use in a clean room, dust and moisture have to be sufficiently removed from the fluid, since they may accumulate in the mechanism, thus hindering the function thereof, causing corrosion of various parts and contaminating the atmosphere in the clean room; and
(3) The above-explained mechanism utilizing static fluid pressure cannot be employed in an apparatus to be used in vacuum, such as the apparatus for laser beam machining or electron beam machining.